I am facing a problem with my flutter app accessing a GATT python endpoint. Sometimes, I do receive the following error message reading a characteristic on my remote machine (RPI 3b):
Unhandled Exception: Exception: GenericFailure<CharacteristicValueUpdateError>(code: CharacteristicValueUpdateError.unknown, message: "GATT exception from MAC='XX:XX:XX:XX:XX:XX', status 1 (GATT_INVALID_HANDLE), type BleGattOperation{description='CHARACTERISTIC_READ'}. (Look up status 0x01 here https://android.googlesource.com/platform/external/bluetooth/bluedroid/+/android-5.1.0_r1/stack/include/gatt_api.h)")

I had a look at the link, but there is just the actual name of the error which is GATT_INVALID_HANDLE. The docs are not quite helpful...
For some reason it does work sometimes after restarting both the GATT server and the app several times.

Does anyone faced such an issue with BLE?

Best and thanks in advance